1. Field of the Invention
This invention relates to snow grooming vehicles that use winches to assist in climbing steep inclines. The invention is also directed to level winding systems for winch assemblies.
2. Description of Related Art
Tracked vehicles used in rugged terrain often employ winch assemblies to assist in maneuvering steep inclines. Snow grooming vehicles, for example, are sometimes equipped with winches that have cables that attach to fixed points on the incline to allow the vehicle to be anchored to the fixed point while sweeping up or down the slope. The cable anchor prevents the vehicle from turning over or sliding down the slope, which could occur on very steep inclines.
A winch-equipped vehicle typically carries a cable that extends outwardly through a rotatable boom. The boom is an elongated metal arm that guides the cable through a series of pulleys. Depending on the direction of intended travel, the boom is rotated to extend forwardly over the cab or to extend rearwardly away from the cab. The cable is typically carried on a drum, preferably a grooved drum, that is driven to control outlay and intake of the cable. A guide, preferably a level winder, is provided at the base of the boom to assist in aligning the cable as it is fed to and from the drum to prevent twisting of the cable.
Most prior art winches use vertical guides and worm gears that follow a linear path parallel to the drum's axis of rotation to align the cable with the drum grooves. As the load on the cable in such a system can be up to 10,000 lbs., the guide assembly must be constructed to accommodate such forces. These assemblies require a large degree of maintenance to prevent the guides and gears from rusting and breaking. However, constant lubrication is necessary. Additionally, these guide assemblies consume a large amount of space, which leaves limited space for the pulleys and rollers associated with the cable system. As a result, the diameter of the pulleys and rollers are often smaller than the minimum recommended cable bending radius. Bending cable about a radius less than the recommended bending radius shortens the life and reliability of the cable.
Some prior art systems use capstan systems to address the problems associated with the prior art guide assemblies described above. FIG. 5 illustrates a capstan system 100 that utilizes a linear guide system 110. The torque applied to the guide system 110 is reduced by winding cable 120 around a capstan 130. As a result, the force at the exit of the capstan 130 is a fraction, 1,000 lbs. for example, of the force in a conventional guide system. The cable 120 is guided from the capstan 130 through a sliding component 140 to a drum 150. However, the capstan 130 itself occupies a great deal of space and is complex, due in large part to the motors required for driving the capstan. Further, maintenance for a capstan is complicated as changing a cable requires a large investment of labor. Moreover, the sliding component 140 must be constantly lubricated.
Thus, there is a need for a less complex and more compact guide assembly associated with such a winch, especially a level winder assembly.